We were thinking of real life applications for physics. One of our ideas was the very scientific act of slowing down a landing space probe or rover. The critical concern for this would be weight, since every pound of landing gear had to be lifted from earth in the first place. Because of this, we decided to find the most efficient means of deceleration with earth similar gravity and atmosphere. The goal of our entire experiment to determine whether a vehicle using air friction or a bumper to slow itself would be more weight efficient. We read about the mars rover's use of air bags, and that helped inspire our designs.
We chose a very time-intensive project, so we designed our experiment to be a sort of a pilot project to a future large experiment. We did not have the time or the materials for finishing the project with enough data for a conclusion, but we did figure out the best way to prepare and build the necessary equipment. We also have data to give us an indication of what the conclusion would be. This would give us a hypothesis. http://www2.jpl.nasa.gov/news/features/images/edl/landing-browse.jpg http://image08.webshots.com/8/4/20/37/115242037MaXMNo_ph.jpg
Here are some images of a simulated mars rover landing. In this case, NASA clearly opted for a bumper method of deceleration instead of air friction.
Procedure
We built two drop vehicles. Both were designed to be the same weight and general size. One would use air friction to slow itself, and the other would have a bumper of sorts to lessen the force of the impact. Both weighed 5.3225 newtons on our force plate. The air friction vehicle was made of: Two 50 liter garbage bags. one men's size 14 shoe box, and ten feet of duct tape, 25 feet of string, two straws, and a few grams worth of wood glue. The bumper vehicle was made of: two aluminum soda cans, a 1 liter ziploc bag full of packing peanuts, a men's size 14 shoe box, a balloon blown up to the maximum capacity, two meter sticks, two rulers, two straws, and twenty feet of duct tape. We used a gram size weight set to get both vehicles to the same weight. we built the air friction vehicle by taping the straws vertically in the center of the longer sides of the shoebox. The straws would hold the shoebox (flat) on the string to keep it on course. One garbage bag was cut into 4 streamers, and one was placed at every corner. We tied 6 feet of string to each corner, and the other end was tied to the secind garbage bag. This served as a parachute of sorts. We also taped the shoe box shut with the duct tape. We taped a 20 gram weight to the top. The bumper vehicle was designed to drop vertically. On the bottom we taped the two soda cans, so they created a round crushable bumper. Below this we taped the bag of packing peanuts. Underneath this we taped the balloon. Two holes were cut on each side, 4 inches from the end of the longest side and inbetween the top and bottom. Through these we attached the meter sticks. The drop vehicle was directly in the middle of the meter sticks. At the end of the meter sticks, we attached the rulers to span the two wings formed by the meter sticks. This created a rigid rectangular frame with the drop vehicle attached in the center. Along the ruler we taped the straws. The point of the wings was to get the straws (which slid on the zipline) away from the body of the vehicle. We had to do this because otherwise the string would have rubbed along the vehicle and created friction. We did not use zipline friction to slow the vehicle because any type of space lander would be falling through air withought the benefit of a brake. The two vehicles were dropped straight down a zipline suspended from a fire escape. at each end, the string was tied to a meter stick so that we could make two parallel lines. the lines led to the ground, and in between them was the force plate. Our vehicles dropped straight down withought spinning or turning and onto the force plate.
Because our project was designed as a guide for a future project, we decided we would have made the following changes: we needed a sign posted to keep small children from destroying our rig; we would have used carabiners instead or straws, because they would have created less friction and they would have been less likely to break; also, this project needs about a week of class time.
Results
We had two data points for each drop vehicle. This is not enough to draw a conclusion on which vehicle slowed better,but it showed that our experiment design was feasible and it indicated that the design of the bumper was superior to the parachute. Given the small sample size, however, this could be false. For the air friction vehicle, the drops created 805 and 754 newtons of force. The vehicle equipped with a bumper dropped with force measured at 639 and 787 newtons. This created a p-value of 0.53. This is too large to draw a conclusion on which vehicle is more efficient. This is not, however, our projects goal. We did prove that our method would get realistic data, which is what we set out to do.
Conclusions
Our project completed our goals. We devised a practical yet precise drop rig, we found two realistic ways of slowing a weight, and we set up a future experiment. If we had more time and people working, we would have been able to greatly increase our sample size. This means that we would be able to lower our p-value. That way, we could determine which, if any, of the methods of deceleration is more weight efficient. A good future experiment would be to follow our designs and build the zipline rig and the two vehicles, then measure enough data for a conclusion.
Table of Contents
Weight Efficiency of Deceleration Designs
George, Sidki
Introduction
We were thinking of real life applications for physics. One of our ideas was the very scientific act of slowing down a landing space probe or rover. The critical concern for this would be weight, since every pound of landing gear had to be lifted from earth in the first place. Because of this, we decided to find the most efficient means of deceleration with earth similar gravity and atmosphere. The goal of our entire experiment to determine whether a vehicle using air friction or a bumper to slow itself would be more weight efficient. We read about the mars rover's use of air bags, and that helped inspire our designs.
We chose a very time-intensive project, so we designed our experiment to be a sort of a pilot project to a future large experiment. We did not have the time or the materials for finishing the project with enough data for a conclusion, but we did figure out the best way to prepare and build the necessary equipment. We also have data to give us an indication of what the conclusion would be. This would give us a hypothesis.
http://www2.jpl.nasa.gov/news/features/images/edl/landing-browse.jpg
http://image08.webshots.com/8/4/20/37/115242037MaXMNo_ph.jpg
Here are some images of a simulated mars rover landing. In this case, NASA clearly opted for a bumper method of deceleration instead of air friction.
Procedure
We built two drop vehicles. Both were designed to be the same weight and general size. One would use air friction to slow itself, and the other would have a bumper of sorts to lessen the force of the impact. Both weighed 5.3225 newtons on our force plate. The air friction vehicle was made of: Two 50 liter garbage bags. one men's size 14 shoe box, and ten feet of duct tape, 25 feet of string, two straws, and a few grams worth of wood glue. The bumper vehicle was made of: two aluminum soda cans, a 1 liter ziploc bag full of packing peanuts, a men's size 14 shoe box, a balloon blown up to the maximum capacity, two meter sticks, two rulers, two straws, and twenty feet of duct tape. We used a gram size weight set to get both vehicles to the same weight. we built the air friction vehicle by taping the straws vertically in the center of the longer sides of the shoebox. The straws would hold the shoebox (flat) on the string to keep it on course. One garbage bag was cut into 4 streamers, and one was placed at every corner. We tied 6 feet of string to each corner, and the other end was tied to the secind garbage bag. This served as a parachute of sorts. We also taped the shoe box shut with the duct tape. We taped a 20 gram weight to the top. The bumper vehicle was designed to drop vertically. On the bottom we taped the two soda cans, so they created a round crushable bumper. Below this we taped the bag of packing peanuts. Underneath this we taped the balloon. Two holes were cut on each side, 4 inches from the end of the longest side and inbetween the top and bottom. Through these we attached the meter sticks. The drop vehicle was directly in the middle of the meter sticks. At the end of the meter sticks, we attached the rulers to span the two wings formed by the meter sticks. This created a rigid rectangular frame with the drop vehicle attached in the center. Along the ruler we taped the straws. The point of the wings was to get the straws (which slid on the zipline) away from the body of the vehicle. We had to do this because otherwise the string would have rubbed along the vehicle and created friction. We did not use zipline friction to slow the vehicle because any type of space lander would be falling through air withought the benefit of a brake. The two vehicles were dropped straight down a zipline suspended from a fire escape. at each end, the string was tied to a meter stick so that we could make two parallel lines. the lines led to the ground, and in between them was the force plate. Our vehicles dropped straight down withought spinning or turning and onto the force plate.
Because our project was designed as a guide for a future project, we decided we would have made the following changes: we needed a sign posted to keep small children from destroying our rig; we would have used carabiners instead or straws, because they would have created less friction and they would have been less likely to break; also, this project needs about a week of class time.
Results
We had two data points for each drop vehicle. This is not enough to draw a conclusion on which vehicle slowed better,but it showed that our experiment design was feasible and it indicated that the design of the bumper was superior to the parachute. Given the small sample size, however, this could be false. For the air friction vehicle, the drops created 805 and 754 newtons of force. The vehicle equipped with a bumper dropped with force measured at 639 and 787 newtons. This created a p-value of 0.53. This is too large to draw a conclusion on which vehicle is more efficient. This is not, however, our projects goal. We did prove that our method would get realistic data, which is what we set out to do.
Conclusions
Our project completed our goals. We devised a practical yet precise drop rig, we found two realistic ways of slowing a weight, and we set up a future experiment. If we had more time and people working, we would have been able to greatly increase our sample size. This means that we would be able to lower our p-value. That way, we could determine which, if any, of the methods of deceleration is more weight efficient. A good future experiment would be to follow our designs and build the zipline rig and the two vehicles, then measure enough data for a conclusion.
Reference
"Entry, Descent, and Landing Innovations for the Mars Exploration Rover Mission." Mars Rover. Nasa. Web. 28 Jan. 2010. <http://marsrover.nasa.gov/technology/is_entry_descent_landing.html>.